Improvement in the art of tunneling



UNITED lSTATES PATENT OFFICE.

DF. TITT C. IIASKIN, OF VALLEJO, CALIFORNIA.

IMPROVEMENT IN THE ART OFTUNNELING.

Specification forming part of Letters Patent No. 147,055, dated February3, 1874; application filed December 9, 1.873.

of the excavation or the infiltration or irruption of water is to beapprehended. Its object is effeetually to prevent such incidents :in acheap and simple way, to which end my improvement consists in fillingthe excavation with compressed air of a density sufficient to resist theinward pressure during the construction of the shell or wall of thetunnel.

The mechanical appliances for carrying out my invention are well knownto engineers, and obviously may be varied in many ways in the details oftheir construction and application to meet the varying conditions underwhich the operations are to be performed, such application, however,involving` nothing more than engineering skill or that of theconstructor.

The accompanyingl drawings represent the best way of carrying out thedetails of my invention now' known to me.

Figure l represents a vertical longitudinal central section through atunnel in process of construct-ion by my improved plan; Fi 2, a verticaltransverse section therethrough on the line A of Fig. l. Fig. 3represents a side elevation, part-ly in section, through the airlock.

In this instance the tunnel is shown as partially completed. Aworking-shaft, a, leads into the tunnelb, which is divided into two ormore compartments by an air-tight diaphragm, bulk-head, or air-lock, d.This air-lock is constructed so as to be movable at pleasure, and is, bypreference, kept up as close to the tunnelhead as convenience willpermit. The com partment or portion of the tunnel in advance of theair-lock forms a workin gchamber or compressed-air chamber, b.Compressed air is forced into this chamber by means of a pipe, g,communicating with a suitable pump, and passing through the air-lock.This pipe is made flexible and extensible in order to accommodate theadjustments of the airlock. The airpump may be located in theworkingchamber, if preferred. A gas-pipe, f, may also be introducedthrough the air-lock. An exitpipe, or waste-pipe, fi, leading from thecompressed-air chamber to the surface, may be used for ventilation or tocarry off waste water, sand, Ste. The air-lock is supplied with valvesor doors 7L to retain the air, while permitting ingress and egress tothe working-chamber.

I make no claim to the special construction of the devices abovedescribed, as they are well known to engineers.

In working by my improved system,the air lock is adjusted in position,the air compressed in the chamber b, and the excavation proceeds in theordinary waybeyond the masonry-work K. The distinguishing feature of mysystem, however, is, that instead of using temporary facings of timberor other rigid material, I rely upon the airpressure to resist thecaving in of the wall or the infiltration of water until the masonrywall is completed.- This pressure is, of course, to be regulated by theexi gencies of the occasion and may be varied from anything above thatof the atmosphere to iifty pounds to the square inch, which is about asmuch as the human system will bear with safety. The effect ol' suchpressure has been found to be to drive water in from the surface of theexcavation, so that the sand becomes dry. In case a jet-seam or smallstream of water is encountered, I supply a temporary shield of canvas,leather, or other light flexible integument to the wall, against whichthe pressure instantly forces it and sea-ls the leak. This device isalso very efficacious in preventing the escape ofthe compressed airthrough leaks in the sides or walls of the excavation. After completingthe masonry walls of large tunnels, I allow the debris (l to accumulatein the bottom, as shown -in Fig. l, until the tunnel is completed,leaving an opening only large enough for working purposes. By this meansthe area of the airlock, the surface exposed to pressure, and theconsequent liability to leaks are materially diminished.

These three features constitute the leading characteristics ofmyinvention, namely: First, the use of compressed air acting directlyupon the excavation walls to prevent leakge or cav 2. The method hereinset forth of preveniing` leakage in the excavation surface of theWorking-chambenby the application thereto of a liexible integument heldin position by atmospheric pressure.

3. The method herein `set forth of partially rei'illingg,` the completedtunnel in advance ot the air-lock7 to diminishthe air-surface thereof.

In testimony whereof l have hereunto sub scribed my name.

D. C. HASKIN. W'itnesscs:

E. C. DAVIDSON, H. Monsns

